1. Field of the Invention
The present invention relates to gas turbine cooled blade turbulators, specifically to turbulators applied to a blade leading edge portion of a gas turbine cooled blade for enhancing heat transfer performance.
2. Description of the Prior Art
FIG. 6, being a longitudinal cross sectional view of a prior art gas turbine moving blade, shows an arrangement of turbulators in cooling air passages thereof and FIG. 7 is a transverse cross sectional view of the gas turbine moving blade of FIG. 6. In these figures, numeral 30 designates a moving blade and cooling passages 31A, 31B, 31C, 31D and 31E are provided therein so that cooling air 33 is supplied into the cooling passages 31A, 31B and 31E, respectively. The cooling air 33 which has entered the cooling passage 31A is discharged from a leading edge portion to effect a shower head cooling 51 as shown in FIG. 7. The cooling air 33 which has entered the cooling passage 31B flows through the cooling passage 31C and further through the cooling passage 31D to be discharged from a blade surface to effect a film cooling 52 as shown in FIG. 7. Also, the cooling air 33 which has entered the cooling passage 31E on a trailing edge side is discharged through a trailing edge to effect a pin fin cooling 53 as shown in FIG. 7.
In each of the cooling passages 31A to 31E, in order to make the cooling air 33 convection-activated and enhance a heat transfer ability, there are provided a multiplicity of oblique turbulators 32, wherein the turbulators 32 are of same shapes arranged obliquely with respect to each of the cooling passages, as shown in FIG. 6.
Also, in FIG. 8 showing a longitudinal cross sectional view of another example of a prior art gas turbine moving blade, numeral 40 designates a moving blade and cooling passages 41A, 41B, 41C, 41D, 41E, 41F and 41G are provided therein so that cooling air 43 is supplied into the cooling passages 41A, 41D and 41E, respectively. The cooling air 43 which has entered the cooling passage 41A is discharged from a leading edge portion to effect a shower head cooling, same as mentioned above. The cooling air 43 which has entered the cooling passage 41D flows through the cooling passages 41C and 41B and the cooling air 43 which has entered the cooling passage 41E flows through the cooling passages 41F and 41G both to be discharged from a blade surface to effect a film cooling. Also, the cooling air 43 which has flown through the cooling passages 41F and 41G is discharged through a trailing edge to effect a pin fin cooling.
In each of the cooling passages 41A to 41G, in order to make the cooling air 43 convection-activated and enhance a heat transfer ability, there are provided a multiplicity of orthogonal turbulators 42, wherein the turbulators 42 are of same shapes arranged orthogonally with respect to each of the cooling passages, as shown in FIG. 8.
As mentioned above, the prior art turbulators of gas turbine cooled blades are made in one kind either of oblique turbulators or of orthogonal turbulators and it is said generally that the oblique turbulators are more excellent in the heat transfer characteristics in the case where the cooling passages have a square cross sectional shape.
Also, of recent papers on the turbulators, one titled, "Heat transfer performance in triangular channels", Zhang et al., 1994, for example, shows a comparison example as shown in FIG. 5, with detailed description made therein being omitted here.
In FIG. 5, cases (a) to (e) are examples where there are provided ribs in the triangular channels, respectively. Case (a) is an example where ribs 61, 62 and 63 are provided separately from each other to inner walls of the triangular channel respectively with angle .alpha.=90.degree., .alpha. being an angle relative to air flow direction. Case (b) is an example where a rib 71 is provided along an entire circumference of the inner wall of the triangular channel likewise with the angle .alpha.=90.degree.. Case (c) is an example where the ribs 61, 62 and 63 are provided separately like the case (a) but obliquely with an angle .beta.&lt;90.degree., .beta. being an angle relative to air flow direction. Case (d) is an example where the rib 71 is provided along the entire circumference of the inner wall like the case (b) but obliquely with the angle .beta.&lt;90.degree. and Case (e) is an example where the ribs 61 and 62 are provided to two sides of the inner wall of the triangular channel obliquely with the angle .beta.&lt;90.degree..
In the mentioned cases (a) to (e), if they are to be shown in the order of good heat transfer coefficient, the order is (a), (b), (c), (d) and (e). Thus, as to the ribs provided on the inner wall of the triangular channel, the case where the ribs 61, 62 and 63 are provided separately on the inner wall with the angle .alpha.=90.degree., as the case (a), is most excellent in the heat transfer coefficient.